SpringBoot的MyBatis简单配置

1. 引入依赖

1.1 修改pom.xml

<!-- mysql 驱动 -->
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.29</version>
</dependency>
<!-- Mybatis -->
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.2.2</version>
</dependency>

1.2 修改配置 application.yml

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mybatis:
  mapper-locations: classpath:mapping/*Mapper.xml
  type-aliases-package: com.summerain0.cloud.common.core.domain.entity

参数讲解

注意 mapper-locations 表示映射文件储存的地方，例如 classpath:mapping/*Mapper.xml 指代resources文件夹下mapping里所有Mapper.xml结尾的文件

type-aliases-package 是实体类所在的位置

自此，MyBatis的引入完成

2. 小小的例子

2.1 建立实体类

import lombok.Data;
import lombok.ToString;

@Data
@ToString
public class SysUser {
    private Integer id;
    private String username;
    private String password;
    private String nick;
}

2.2 建立映射类

@Repository
public interface UserMapper {
    SysUser findById(int id);
}

同时在resources的mapping文件里建立一个和映射类同名的xml文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.summerain0.cloud.system.mapper.UserMapper">

    <resultMap id="SysUser" type="com.summerain0.cloud.common.core.domain.entity.SysUser">
        <result column="id" jdbcType="INTEGER" property="id"/>
        <result column="username" jdbcType="VARCHAR" property="username"/>
        <result column="password" jdbcType="VARCHAR" property="password"/>
        <result column="nick" jdbcType="VARCHAR" property="nick"/>
    </resultMap>

    <select id="findById" resultType="com.summerain0.cloud.common.core.domain.entity.SysUser">
        select *
        from sys_user
        where id = #{id}
    </select>

</mapper>

2.3 建立测试方法

public interface UserService {
    SysUser findById(int id);
}

@Service
public class IUserService implements UserService {
    private UserMapper userMapper;

    @Override
    public SysUser findById(int id) {
        return userMapper.findById(id);
    }

    @Autowired
    public void setUserMapper(UserMapper userMapper) {
        this.userMapper = userMapper;
    }
}

2.4 提供接口

@RestController
public class TestController {
    private IUserService userService;

    @RequestMapping("/test")
    public String test() {
        return userService.findById(3).toString();
    }

    @Autowired
    public void setUserService(IUserService userService) {
        this.userService = userService;
    }
}

2.5 测试结果

运行结果

3. 常见问题

3.1 找不到Mapper？

在启动类加入@MapperScan(“com.summerain0.cloud.system.mapper”)即可

@MapperScan("com.summerain0.cloud.system.mapper")
@SpringBootApplication
public class CloudApplication {
    public static void main(String[] args) {
        SpringApplication.run(CloudApplication.class, args);
    }
}